The major goal of this study is to further our understanding of the relationship between temperament and childhood mood and behavioral disorders. Symptoms of child psychopathology (e.g., depression, oppositional behaviors) are dysfunctional, excessive, maladaptive, or debilitating and they cause problems for children. This study is informed by findings from genetic, biological and behavioral levels of analysis. The principal hypothesis of the proposed study is that the emotion-modulated startle mediates the association between temperament and symptoms of psychopathology in children. We know from animal studies that affective forebrain regions modulate the magnitude of the startle response. Startle is amplified during negative, and attenuated during positive emotional states. Thus, startle becomes a marker for activation of affective brain circuitry. In addition, startle magnitude is influenced by both temperamental type and symptoms of psychopathology, making it a useful tool in understanding processes involved in the relationship. This study will expand the repertoire of methods available for the study of emotion in children. Advantages of the emotion-modulated startle over other measures of emotion include its sensitivity to moderate levels of emotion that are not readily observed in behavior and relative independence from the eliciting circumstance. It is not vulnerable to rater biases or affected by display rules. Acoustic startle probes will be embedded into emotion-eliciting videoclips and startle magnitude will be coded from videotape. Behavioral coding of the startle response is an effective method that does not require electromyographic measurement and thus may economically be used in naturalistic settings with large developmental samples. Results will clarify the role of emotion-modulated startle for the temperament/symptom relationship, expand our methods of studying emotion in children, and identify biobehavioral markers of child psychopathology useful in elucidating gene function. In addition, results provide a first-step in a more extensive research program that works to inform diagnosis, prevention, and treatment of child psychopathology. [unreadable] [unreadable] [unreadable]